1. Field of the Invention
The present invention relates to a method and system for determining the shape in a plane to be determined in atmosphere of scattering materials. More particularly the present invention relates to a method for determining the shape in a plane to be determined to which light-section method is applied in such atmosphere where scattering materials such as dust, mist and the like float as in the case of the interior of the top of a blast furnace.
2. Description of the Prior Art
Heretofore, light-section method has been known as a method for determining a position, shape, dimension, displacement and the like of an object to be determined. In the case of determining the shape in a plane to be determined by utilizing such light-section method, the operation is carried out, as illustrated in FIG. 1, in accordance with such manner that a projector 2 and a pick up means 4 are employed, light is irradiated on a line 8 to be determined being imagined on a plane 6 to be determined by means of the projector 2, the line 8 to be determined is picked up by means of the pickup means 4, and the shape in the plane to be determined is obtained on the basis of the picture picked up. More specifically, first, either a certain plane (light cut section) a b c is scanned by means of light beam emitted from a point a in the projector 2 at a prescribed rate, or belt-like light rays are irradiated onto such certain plane to illuminate the line 8 to be determined, and the line 8 is picked up by utilizing the pickup means 4 placed outside the certain plane a b c. The line 8 to be determined is picked up as an image of light locus in the case where scanning is effected with light beam, whilst the line 8 is picked up as a luminance line image along the line to be determined in the case where belt-like light rays are irradiated. Then, two-dimensional position coordinates of the respective points of an image of line to be determined on the picture picked up are extracted, and further three-dimensional position coordinates in the respective points of the line to be determined on the plane to be determined are extracted from the resulting two-dimensional position coordinates and a geometrical arrangement defined by the certain plane a b c and the pickup means by means of coordinate conversion. Furthermore a plurality of lines to be determined are imagined on the plane 6 to be determined, light is irradiated on the respective lines to be determined by varying an azimuth of the certain plane a b c, and three-dimensional position coordinates in the respective points of the respective lines to be determined in accordance with a similar manner to that mentioned above. Then, when enveloping surface is extracted from these three-dimensional position coordinates, the shape in the plane to be determined can be obtained.
However, since such light-section method utilizes light, if environmental condition of such determination is in atmosphere of scattering materials, there arises such disadvantage that a part of the light projected on the plane to be determined is scattered by floating scattering materials, and when the line to be determined is picked up in this condition, a background picture (image of scattered light) is picked up other than the image of line to be determined. Thus, there arise such problems in that such background picture changes its distribution of luminance in response to the change in a distribution of spatial and time concentration of scattering materials, and generation of such background picture results in deterioration in SN ratio of the image of line to be determined, very difficult detection, or such a case where the background picture is erroneously detected as the image of line to be determined. When these phenomena are described in conjunction with a blast furnace, there cause such problems that laser beam does not reach the plane to be determined, and that picking up of luminous spots or luminous lines on the plane to be determined becomes difficult in the case where a dust density is very high either immediately after charging a raw material into the blase furnace in which a Bell type charging means is utilized, or during charging of the raw material into the blast furnace in which a Bell-less type charging means is employed.
Moreover, in the case when a profile in the stock surface of charge in the top of a blast furnace is determined, emission from the core of the furnace frequently occurs, such emission is picked up as a passive image, such passive image functions similarly to the case of the above-mentioned background picture so that there arise similar problems to those as mentioned above.